Wet type scrubber for exhaust gas and method of operation

ABSTRACT

A wet type scrubber for exhaust gas includes a wet scrubbing chamber which is disposed such that the exhaust gas introduced through an inlet flows horizontally toward an outlet and includes an overflow opening formed at a position in a side surface thereof spaced apart by a certain distance upwardly from the bottom thereof an eliminator which is disposed within the wet scrubbing chamber and installed such that the bottom thereof is positioned below the overflow opening, and includes a plurality of bent blades arranged to form a passage for the exhaust gas; an oil/water separation tank for scrubbing liquid received from the overflow opening by sequentially passing the liquid through a plurality of reservoirs, and a spray nozzle installed to spray the liquid into an inlet-side space of the wet scrubbing chamber.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application is a continuation application under 35 U.S.C. § 365(c) of International Application No. PCT/KR2005/003233, filed Sep. 29, 2005 designating the United States. International Application. No. PCT/KR2005/003233 was published in English as WO2006/104304 A1 on Oct. 5, 2006. This application further claims the benefit of the earlier filing dates under 35 U.S.C. § 365(b) of Korean Patent Application No. 10-2005-0026074 filed Mar. 29, 2005. This application incorporates herein by reference the International Application No. PCT/KR2005/003233 including the International Publication No. WO2006/104304 A1 and the Korean Patent Application No. 10-2005-0026074 in their entirety.

BACKGROUND

The present disclosure relates to an apparatus for scrubbing exhaust gas, and more particularly, to a wet type scrubbing apparatus.

A wet type scrubber is provided for wet-scrubbing gases exhausted from industrial sites. The wet type scrubber for exhaust gas removes dust or noxious substances contained in exhaust gas.

SUMMARY

One aspect of the invention provides a wet scrubbing system, which comprises: a chamber installed with a plurality of blades defining a plurality of passages for the moisturized exhaust gas to travel therethrough, wherein the plurality of blades are configured to contact traveling moisturized exhaust gas so as to precipitate at least part of the moisturized exhaust gas into liquid, wherein the chamber is configured to hold the liquid in a bottom portion thereof; and a liquid overflow outlet configured to let the liquid held in the bottom portion of the chamber to reach a level and begin to overflow when the liquid reached the level such that traveling of the moisturized exhaust gas under the plurality of blades is substantially inhibited when the liquid reached the level.

In the foregoing system, the system may further comprise liquid in the bottom portion of the chamber, wherein the liquid is approximately at the level. Each blade may comprise a top end and a bottom end, wherein the level is higher than the bottom end. The liquid in the bottom portion may contact at least part of the plurality of blades. Substantially all the moisturized exhaust gas may be configured to travel through the plurality of passages when the liquid is at the level. The system may further comprise a liquid drain on a bottom surface of the chamber, wherein the liquid drain may be configured to drain the liquid that is under the level. The system may further comprise a liquid sprayer configured to spray liquid particles onto a stream of exhaust gas so as to form the moisturized exhaust gas. The liquid sprayer may be installed within the chamber and is located upstream the plurality of blades.

Another aspect of the invention provides a wet scrubbing system, which comprise: a liquid sprayer configured to spray liquid particles to a stream of exhaust gas so as to form moisturized exhaust gas; a chamber installed with a plurality of blades configured to provide a plurality of surfaces for at least part of the moisturized exhaust gas to contact thereto and to precipitate into liquid, wherein the chamber is configured to hold the liquid in a bottom portion thereof; a liquid overflow outlet configured to let the liquid held in the bottom portion of the chamber to reach a level and begin to overflow when the liquid reached the level; and a liquid drain on a bottom surface of the chamber, wherein the liquid drain is configured to drain the liquid that is under the level.

In the foregoing system, the plurality of blades defines a plurality of passages for the moisturized exhaust gas to travel therethrough, wherein traveling of the moisturized exhaust gas under the plurality of blades is substantially inhibited when the liquid reached the level. Substantially all the moisturized exhaust gas may be configured to travel through the plurality of passages when the liquid is at the level. The system may further comprise liquid in the bottom portion of the chamber, wherein the liquid is approximately at the level. Each blade may comprise a top end and a bottom end, wherein the level may be higher than the bottom end. The liquid in the bottom portion may contact at least part of the plurality of blades. The liquid sprayer may be installed within the chamber and is located upstream the plurality of blades.

Still another aspect of the invention provides a wet scrubbing method, which comprise: flowing moisturized exhaust gas through a plurality of blades installed in a chamber, wherein while flowing at least part of the moisturized exhaust gas precipitates into liquid and drops to a bottom portion of the chamber; and maintaining the liquid in the bottom portion at a level sufficient to substantially inhibit traveling of the moisturized exhaust gas under the plurality of blades.

In the foregoing method, the method may further comprise overflowing the liquid when the liquid reaches the level. The method may further comprise spraying liquid particles onto a stream of exhaust gas so as to form the moisturized exhaust gas. The method may further comprise draining the liquid such that a portion of the liquid under the level is drained. The plurality of blades may define a plurality of passages for the moisturized exhaust gas to travel therethrough within the chamber, wherein traveling moisturized exhaust gas may contact a surface of the blades, thereby precipitating into liquid. The chamber may comprise a liquid overflow outlet, which allows the liquid to overflow when the liquid reaches the level.

An aspect of the present invention is to provide a scrubber capable of improving the efficiency of removal of dust, mist, moisture, condensate and the like from exhaust gas.

Furthermore, another aspect of the present invention is to provide a wet type scrubber capable of preventing generation of wastewater and preventing clogging of spray nozzles in a scrubbing chamber by changing the structure of an oil/water separation tank.

One aspect of the invention provides a wet type scrubber for exhaust gas comprises a wet scrubbing chamber which includes an inlet through which the exhaust gas is introduced, an outlet through which treated exhaust gas flows out, and an overflow opening formed at a position in a side surface thereof spaced apart by a certain distance upwardly from the bottom thereof, and is disposed such that the exhaust gas introduced through the inlet flows horizontally toward the outlet; an eliminator which is disposed within the wet scrubbing chamber to divide the interior of the wet scrubbing chamber into an inlet-side space and an outlet-side space and installed such that the bottom thereof is positioned below the overflow opening, and includes a plurality of bent blades arranged to form a passage for the exhaust gas; an oil/water separation tank including a plurality of reservoirs to scrub liquid received from the overflow opening by sequentially passing the liquid through the plurality of reservoirs; a spray nozzle installed to receive liquid from a final treatment reservoir of the reservoirs of the oil/water separation tank and to spray the liquid into the inlet-side space of the wet scrubbing chamber; a concentrating tank for receiving sludge precipitated in the oil/water separation tank and concentrating the sludge therein; and a dehydrator for receiving the concentrated sludge from the concentrating tank, separating remaining liquid from the concentrated sludge, supplying the separated liquid to the final treatment reservoir of the oil/water separation tank, and discharging a cake of sludge obtained through the separation of the remaining liquid.

When acid exhaust gas is intended to be treated by the wet type scrubber of the present invention, the wet type scrubber can scrub the acid exhaust gas by further comprising a pH sensor installed at the oil/water separation tank, an alkali chemical storage tank, a chemical feed pump connected to the storage tank to feed an alkali chemical to the oil/water separation tank, and a controller for receiving a value measured by the pH sensor and supplying the chemical to the final treatment reservoir by operating the chemical feed pump if the measured value is in a predetermined range.

Preferably, the plurality of blades of the eliminator are vertically disposed such that moisture or dust removed from the exhaust gas easily falls onto the bottom of the wet scrubbing chamber by gravity. Further, in order to improve the efficiency of removal of contaminants by the eliminator, it is preferred that a plurality of eliminators be arranged to be spaced apart from one another at a predetermined interval, and a plurality of nozzles be provided and at least one of the nozzles be installed between the eliminators.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a wet type scrubber according to an embodiment of the present invention.

FIG. 2 is a schematic view of a wet type scrubber according to another embodiment of the present invention.

FIG. 3 a perspective view of an example of an eliminator used in the wet type scrubber according to the present invention.

FIG. 4 shows various arrangement states of spray nozzles and eliminators in the wet type scrubber according to the present invention.

FIG. 5 is a schematic view of an exemplary wet type scrubber.

Following are representative elements appearing on the drawings and their reference numerals.

10: Scrubbing chamber 11: Eliminator 20: Oil/water separation tank 50: Concentrating tank 70: Dehydrator 80: Chemical tank 81: pH sensor

DETAILED DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a schematic view of a wet type scrubber according to an embodiment of the present invention. The wet type scrubber of this embodiment comprises a wet scrubbing chamber 10 with an inlet 17 through which exhaust gas is introduced and an outlet 12 through which treated exhaust gas flows out; a pair of eliminators 11 disposed within the wet scrubbing chamber to divide the interior of the wet scrubbing chamber into an inlet-side space and an outlet-side space; an oil/water separation tank 20 comprising a plurality of reservoirs for scrubbing liquid containing dust and the like discharged from the wet scrubbing chamber 10; a concentrating tank 50 for concentrating sludge precipitated in the oil/water separation tank 20; and a dehydrator 70 for separating moisture from the concentrated sludge. Additionally, the wet type scrubber of this embodiment comprises spray nozzles 18 installed to spray liquid into the inlet-side space of the wet scrubbing chamber 10.

An installation stand 14 is fixed at a lower portion of the wet scrubbing chamber 10 so as to install the eliminators such that the eliminators are spaced apart by a predetermined distance from the bottom of the wet scrubbing chamber 10. Furthermore, the wet scrubbing chamber 10 is disposed such that exhaust gas introduced into the wet scrubbing chamber through the inlet 17 flows horizontally toward the outlet 12, and the eliminators 11 are installed perpendicularly to the flow of the exhaust gas. Furthermore, an overflow opening 13 for drainage of liquid collected on the bottom of the wet scrubbing chamber 10 is formed at a position on a side wall of the wet scrubbing chamber 10, which corresponds to a level higher than that of the bottoms of the eliminators 11. Furthermore, a drainpipe 15 for cleaning is connected to the bottom of the wet scrubbing chamber 10, and a valve 16 for closing the drainpipe 15 upon use of the wet scrubbing chamber is installed at the drainpipe 15.

The eliminators 11 installed in the wet scrubbing chamber 10 are disposed within the wet scrubbing chamber 10 to divide the scrubbing chamber 10 into the inlet-side space and the outlet-side space. The eliminators 11 are installed such that the bottoms thereof are mounted on the installation stand 14 positioned below the overflow hole 13 and side surfaces of the eliminators 11 except the bottoms thereof are in close contact with an inner surface of the wet scrubbing chamber 10. Therefore, moisture separated from exhaust gas, which passes through the eliminators 11, flows to and is collected at the lower portion of the wet scrubbing chamber 10, and the collected moisture is discharged to a first reservoir 20 a of the oil/water separation tank 20 through a drainpipe 19 connected to the overflow opening 13. Since the bottoms of the eliminators 11 are positioned below the overflow opening 13, water or a chemical solution is always filled in a space between the bottoms of the eliminators 11 and the bottom of the wet scrubbing chamber 10 so that the exhaust gas cannot pass through the space. Therefore, the exhaust gas is exhausted through the outlet 12 in a state where moisture is always removed from the exhaust gas through the eliminators 11.

FIG. 3 a perspective view of an example of an eliminator used in the wet type scrubber according to one embodiment of the present invention. Referring to FIG. 3, the eliminator 11 comprises an upper plate 11 a with handles installed thereon, a frame 11 d for receiving a plurality of blades 11 b, a lower plate 11 c, and the plurality of blades 11 b installed at the upper plate 11 a and the lower plate 11 c. The plurality of blades 11 b are vertically disposed so that moisture or dust removed from the exhaust gas falls onto the bottom of the wet scrubbing chamber 10 by gravity. Furthermore, the respective blades 11 b are bent so that particulates can be removed by guiding a flow direction of the exhaust gas. Moreover, installation grooves 11 c-1 in which the blades 11 b are installed are formed in the upper plate 11 a and the lower plate 11 c.

FIG. 4 shows various arrangement states of the spray nozzles and the eliminators in the wet type scrubber according to one embodiment of the present invention. The spray nozzles 18 may be installed (contrary to those shown in FIG. 1) such that a liquid spray direction of the spray nozzles faces in a downstream direction of the flow of exhaust gas (a direction designated by arrows) as shown in FIG. 4 a, pairs of spray nozzles 18 may be installed such that spray directions thereof are opposite to each other as shown in FIG. 4 b, or spray nozzles may be installed between the plurality of eliminators 11 as shown in FIG. 4 c.

Dust or moisture removed by the eliminators 11 fall into the first reservoir 20 a of the oil/water separation tank 20 through the overflow opening of the wet scrubbing chamber 10. The oil/water separation tank 20 comprises the plurality of reservoirs 20 a to 20 f of which partitions walls are formed with penetration holes such that supernatant and subnatant alternately flow from one of the reservoirs to a neighboring reservoir through the penetration holes so as to precipitate sludge. Therefore, particles such as dust are all precipitated in intermediate reservoirs so that scrubbed clean supernatant can flow out from the final reservoir 20 f. A pump 30 is connected to the final reservoir 20 f through a pipe 31, and the pump supplies scrubbed water or a scrubbed solution to the spray nozzles 18 installed in the wet scrubbing chamber 10. Accordingly, the spray nozzles 18 are prevented from being clogged.

Natural flow piping or a pump 40 for discharging the precipitated sludge is connected to the bottoms of the respective reservoirs of the oil/water separation tank 20. In case of the pump 40, the pump sucks the sludge and feeds it to the concentrating tank 50. The sludge concentrated in the concentrating tank 50 is sent to the dehydrator 70 through a pump 60 connected to a pipe 61. The dehydrator 70 separates remaining liquid from the sludge and sends it to the final reservoir 20 f of the oil/water separation tank 20, and separately discharges a cake of sludge that is to be disposed of. Reference numeral 90 that has not yet been described is a blower for sucking the exhaust gas and exhausting it through a chimney 100.

The wet type scrubber for exhaust gas according to this embodiment is preferably used in industrial sites where a large amount of dust is discharged. In this case, water is preferably used as liquid sprayed from the nozzles. In the wet type scrubber of this embodiment, the entire exhaust gas containing the sprayed moisture passes through the eliminators and is then exhausted through the outlet in a state where the moisture has been removed from the exhaust gas, thereby preventing excessive loss of moisture. Therefore, there is a little need for replenishment of a solution to be sprayed. Moreover, in the wet type scrubber of this embodiment, clogging of the nozzles due to sludge is prevented by completely scrubbing the sludge in the oil/water separation tank. Further, since the sludge is separately concentrated and discharged in a form of a cake and a solution is circulated and then reused, wastewater is not discharged, resulting in a contribution to environmental conservation.

FIG. 2 is a schematic view of a wet type scrubber according to another embodiment of the present invention. The wet type scrubber for exhaust gas according to this embodiment is different from the wet type scrubber for exhaust gas shown in FIG. 1 in that for neutralization of acid exhaust gas in the wet scrubbing chamber 10, it further comprises a device for spraying an alkaline solution through the spray nozzles 18.

For instance, in case of acid exhaust gas, the exhaust gas contains SOx, NOx, HCl, and/or other hazardous substances. In order to treat the acid exhaust gas by the wet type scrubber, the acid exhaust gas is neutralized by spraying an alkaline chemical to the exhaust gas such that the alkaline chemical comes into contact with the exhaust gas, and moisture and dust are removed from the exhaust gas by passing the exhaust gas through the eliminators. Although a calcium based (Ca(OH)₂, CaO and CaCO₃) solution and a sodium based (NaHCO₃, NaOH and Na₂CO₃) solution can be used as the alkaline chemical, the sodium based solution is preferably used since upon use of the calcium based solution, a reaction product has low solubility as compared with the sodium based solution, resulting in formation of a great deal of scale in a reactor due to precipitation.

If sodium hydroxide (NaOH) is used as a chemical in the wet treatment process, acid exhaust gas is neutralized according to the following reaction equations 1 to 4. Although sulfur dioxide or hydrogen chloride easily dissolved in water or an alkaline solution is easily removed in the wet treatment process, NO, dioxin and other hazardous gases that are not easily dissolved in water or an alkaline solution are hardly removed in the wet treatment process but exhausted as they are. Thus, there is a need for an additional treatment process. Dust is removed by inertial impaction with droplets of a sodium hydroxide solution sprayed from the nozzles in the wet scrubbing chamber or interception by particles of the droplets, and fine particles are removed while passing through the eliminators by colliding with the droplets due to diffusion resulting from Brownian movement, and other gravity, electric force, and the like.

[Reaction Equation 1]

SO2+2NaOH

Na2SO3+H2O

[Reaction Equation 2]

SO2+NaOH

NaHSO3

[Reaction Equation 3]

HCl+2NaOH

NaCl+H2O

[Reaction Equation 4]

NO+2NaOH+½O2

Na2(NO3)2

In addition to the elements of the scrubber shown in FIG. 1, the wet type scrubber for exhaust gas according to this embodiment further comprises a unit for adding sodium hydroxide (NaOH) with a properly modified pH value to a solution to be sprayed so as to neutralize the acid exhaust gas and remove hazardous particle substances such as dust contained in the exhaust gas. That is, the wet type scrubber of this embodiment further comprises a chemical storage tank 80 for storing an alkaline chemical therein, a pH sensor 81 installed in the reservoir 20 f of the oil/water separation tank 20, and a chemical feed pump 83 and pipes 82 and 84 for feeding the chemical stored in the chemical storage tank 80 to the reservoir 20 f. Moreover, although not shown in FIG. 2, the wet type scrubber of this embodiment further comprises a controller for receiving a value measured by the pH sensor 81 and supplying the chemical to the final treatment reservoir 20 f by operating the chemical feed pump if the measured value is in a predetermined range. Typically, a programmable logic controller (PLC) or a general-purpose computer can be used as the controller.

The operation of the wet type scrubber for exhaust gas according to this embodiment will be described below. A pipe for use in transferring exhaust gas is connected to the inlet 17 of the wet scrubbing chamber 10 and the blower 90 is operated, so that the exhaust gas can be introduced into the wet scrubbing chamber 10 through the inlet 17 of the wet scrubbing chamber 10. The introduced exhaust gas is neutralized by reacting with a solution into which an alkaline chemical sprayed from the spray nozzles 18 is dissolved, according to the reaction equations 1 to 4.

The neutralized exhaust gas passes through the eliminators 11 where dust or moisture is removed therefrom exhaust gas, and is then exhausted through the outlet 12. Dust, neutralized salts, moisture and condensate contained in the exhaust gas, which have been removed by the eliminators 11, are collected on the bottom of the wet scrubbing chamber 10. A solution with the chemical dissolved therein is always filled in a space between the bottoms of the eliminators 11 and the bottom of the wet scrubbing chamber 10 so that the exhaust gas cannot pass through the space. Therefore, the exhaust gas is exhausted through the outlet 12 in a state where dust or moisture is always removed from the exhaust gas through the eliminators 11.

The moisture, which flows to and is collected on the bottom of the wet scrubbing chamber 10, is discharged to the first reservoir 20 a of the oil/water separation tank 20 through the drainpipe 19 connected to the overflow opening 13. Dust and reaction salts contained in the solution are precipitated onto the bottom of the oil/water separation tank 20 while the solution is sequentially scrubbed in the oil/water separation tank 20. Sludge precipitated onto the bottom of the oil/water separation tank 20 is sent to the concentrating tank 50 through the pump 40, and the sludge is concentrated in the concentrating tank. The concentrated sludge is dehydrated in the dehydrator 70, and a cake of sludge is then discharged and disposed of. A solution collected through dehydration in the dehydrator 70 is sent to and reused in the oil/water separation tank 20. If a value measured by the PH sensor 81 installed at the oil/water separation tank 20 is out of a predetermined range, a controller (not shown) operates the pump 83 so that the chemical stored in the tank 80 can be supplied to the oil/water separation tank 20.

In the wet type scrubber for exhaust gas according to an embodiment of the present invention, the overflow opening is formed at a position higher than the bottoms of the eliminators installed in the wet scrubbing chamber, so that moisture and dust of exhaust gas can be more efficiently removed. Furthermore, a solution containing the dust removed from the exhaust gas is scrubbed in the oil/water separation tank comprising a plurality of treatment reservoirs, thereby preventing the nozzles from being clogged. Furthermore, remaining liquid contained in sludge discharged from the oil/water separation tank is separated by the dehydrator and then reused. Thus, wastewater is not discharged, resulting in a contribution to environmental conservation.

As shown in FIG. 5, when the level of the liquid is below the bottom of the blades, some of the exhaust gas can travel under the blades, and therefore may decrease the scrubbing efficiency. Maintaining the liquid about or higher than the bottom of the blades substantially inhibits traveling of the moisturized exhaust gas under the blades, and therefore would improve the scrubbing efficiency.

It should be understood that the spirit of the present invention is not limited to the embodiments described and illustrated herein. The scope of the present invention is defined only by the appended claims. It is apparent to those skilled in the art that various modifications and changes can be made thereto within the spirit of the invention. Therefore, the modifications and changes will fall within the scope of the present invention so long as they are apparent to those skilled in the art. 

1. A wet scrubbing system comprising: a chamber installed with a plurality of blades defining a plurality of passages for the moisturized exhaust gas to travel therethrough, wherein the plurality of blades are configured to contact traveling moisturized exhaust gas so as to precipitate at least part of the moisturized exhaust gas into liquid, wherein the chamber is configured to hold the liquid in a bottom portion thereof; and a liquid overflow outlet configured to let the liquid held in the bottom portion of the chamber to reach a level and begin to overflow when the liquid reached the level such that traveling of the moisturized exhaust gas under the plurality of blades is substantially inhibited when the liquid reached the level.
 2. The system of claim 1, further comprising liquid in the bottom portion of the chamber, wherein the liquid is approximately at the level.
 3. The system of claim 2, wherein each blade comprises a top end and a bottom end, wherein the level is higher than the bottom end.
 4. The system of claim 2, wherein the liquid in the bottom portion contacts at least part of the plurality of blades.
 5. The system of claim 1, wherein substantially all the moisturized exhaust gas is configured to travel through the plurality of passages when the liquid is at the level.
 6. The system of claim 1, further comprising a liquid drain on a bottom surface of the chamber, wherein the liquid drain is configured to drain the liquid that is under the level.
 7. The system of claim 1, further comprising a liquid sprayer configured to spray liquid particles onto a stream of exhaust gas so as to form the moisturized exhaust gas.
 8. The system of claim 7, wherein the liquid sprayer is installed within the chamber and is located upstream the plurality of blades.
 9. A wet scrubbing system comprising: a liquid sprayer configured to spray liquid particles to a stream of exhaust gas so as to form moisturized exhaust gas; a chamber installed with a plurality of blades configured to provide a plurality of surfaces for at least part of the moisturized exhaust gas to contact thereto and to precipitate into liquid, wherein the chamber is configured to hold the liquid in a bottom portion thereof, a liquid overflow outlet configured to let the liquid held in the bottom portion of the chamber to reach a level and begin to overflow when the liquid reached the level; and a liquid drain on a bottom surface of the chamber, wherein the liquid drain is configured to drain the liquid that is under the level.
 10. The system of claim 9, wherein the plurality of blades defines a plurality of passages for the moisturized exhaust gas to travel therethrough, wherein traveling of the moisturized exhaust gas under the plurality of blades is substantially inhibited when the liquid reached the level.
 11. The system of claim 10 wherein substantially all the moisturized exhaust gas is configured to travel through the plurality of passages when the liquid is at the level.
 12. The system of claim 9, further comprising liquid in the bottom portion of the chamber, wherein the liquid is approximately at the level.
 13. The system of claim 12, wherein each blade comprises a top end and a bottom end, wherein the level is higher than the bottom end.
 14. The system of claim 12, wherein the liquid in the bottom portion contacts at least part of the plurality of blades.
 15. The system of claim 9, wherein the liquid sprayer is installed within the chamber and is located upstream the plurality of blades.
 16. A wet scrubbing method comprising: flowing moisturized exhaust gas through a plurality of blades installed in a chamber, wherein while flowing at least part of the moisturized exhaust gas precipitates into liquid and drops to a bottom portion of the chamber; and maintaining the liquid in the bottom portion at a level sufficient to substantially inhibit traveling of the moisturized exhaust gas under the plurality of blades.
 17. The method of claim 16, further comprising overflowing the liquid when the liquid reaches the level.
 18. The method of claim 16, further comprising spraying liquid particles onto a stream of exhaust gas so as to form the moisturized exhaust gas.
 19. The method of claim 16, further comprising draining the liquid such that a portion of the liquid under the level is drained.
 20. The method of claim 16, wherein the plurality of blades define a plurality of passages for the moisturized exhaust gas to travel therethrough within the chamber, wherein traveling moisturized exhaust gas contacts a surface of the blades, thereby precipitating into liquid.
 21. The method of claim 20, wherein the chamber comprises a liquid overflow outlet which allows the liquid to overflow when the liquid reaches the level. 